A combination weighing and packing device of this type is disclosed, for example, in the opened Japanese patent specification No. 59-46821. The weighing section of this device delivers batches of product, such as cornflakes, each batch having a degree of swell which may vary according to manufacturing conditions. Thus the apparent specific gravity of the batches may vary significantly. In the packing section, each batch is introduced into a transparent cylinder and a wrapping film is also introduced therein to wrap the batch by closing the top and bottom ends thereof. The transparent cylinder is provided with photoelectric detectors each comprising light-emitting and sensing elements for detecting the height of wrapped product representative of the volume of product. The detected height is used for controlling the acceptable weight in the next cycle of combination selecting operation.
In the above-cited device, the photoelectric detectors are disposed in the packing section and tend to undesirably complicate its structure together with its sophisticated packing mechanism. Another disadvantage of such photoelectric detectors is that it is difficult to interface weighing and packing devices of this type designed and manufactured separately by different vendors (as is usually the case), since the outputs of the photoelectric detectors are to be fed back from the packing device to the weighing device for controlling the target weight.
Accordingly, an object of this invention is to provide a combination weighing device which is equipped to detect the volume of product selected in each combination to control the target weight.